In recent years, with development of information equipment, the needs for low-power and thin display apparatus have grown, so that extensive study and development have been made on display apparatuses fitted to these needs. Of these display apparatuses, a liquid crystal display apparatus has been developed actively as a display apparatus capable of meeting the needs by electrically controlling alignment of liquid crystal molecules to change optical characteristics-of the liquid crystal and has been brought into the commercial stage.
From the viewpoints of low power consumption and alleviation of eyestrain, reflection-type display apparatuses, an electrophoretic display device wherein charged particles dispersed in an insulating solvent are moved between electrodes to effect display, has been proposed in Japanese Laid-Open Patent Application (JP-A) Hei 9-185087 and Japanese Patent No. 2551783.
As basic drive schemes of the electrophoretic display device, a scheme wherein charged particles (electrophoretic particles) are moved in a horizontal direction as shown in FIG. 1 and a scheme wherein charged particles are moved in a vertical direction as shown in FIG. 2, have been proposed. In either of these schemes, a dispersion liquid comprising charged particles and a dispersion medium is used as a display medium. Further, there has been also provided an electrophoretic display device using microcapsules each containing charged particles and a dispersion medium as a display medium as shown in FIG. 3.
In the respective structures of these electrophoretic display devices, electrophoretic particles are moved depending on a charge polarity of the electrophoretic particles and a polarity of a voltage applied to both electrodes. As a result, different states in position of the electrophoretic particles are optically recognized to cause a contrast.
In the electrophoretic display devices, stable control of migration of the charged electrophoretic particles is important for display performances in terms of a high contrast and durability performances.
With respect to the electrophoretic particles for use in the electrophoretic display devices, JP-A Hei 3-249736, JP-A Hei 3-249737, JP-A Hei 3-249738, JP-A Hei 3-249739, and JP-A Hei 4-166918 have been proposed. Further, U.S. Pat. No. 6,590,696 has been proposed with respect to the dispersion liquid.
However, in the conventional electrophoretic display devices, chargeability and dispersibility of the electrophoretic particles are insufficient, so that these arises such a problem that a stable image cannot be retained.